The following substances are exposed to air:
magnesium chloride, quicklime, copper nitrate crystals, washing soda, conc. sulphuric acid, sodium chloride, silica ge
Which of the above will (a) lose weight
(b) gain weight
(c) remain the same.
Name and define the phenomena that accounts for the gain or loss in weight of the substances in (i)
Please answer the second part fast
Answers
Explanation:
Copper(II) nitrate, Cu(NO3)2, is an inorganic compound that forms a blue crystalline solid. Anhydrous copper nitrate forms deep blue-green crystals and sublimes in a vacuum at 150-200 °C. Copper nitrate also occurs as five different hydrates, the most common ones being the trihydrate and hexahydrate. These materials are more commonly encountered in commerce than in the laboratory.
Quick Facts: Names, Identifiers ...
Synthesis and reactions for copper nitrate
Aqueous solution of copper(II) nitrate.
Hydrated copper nitrate can be prepared by hydration of the anhydrous material or by treating copper metal with an aqueous solution of silver nitrate or concentrated nitric acid:
Cu + 4 HNO3 → Cu(NO3)2 + 2 H2O + 2 NO2
Anhydrous Cu(NO3)2 forms when copper metal is treated with N2O4:
Cu + 2 N2O4 → Cu(NO3)2 + 2 NO
Attempted dehydration of any of the hydrated copper(II) nitrates by heating instead affords the oxides, not Cu(NO3)2. At 80 °C, the hydrates convert to "basic copper nitrate" (Cu2(NO3)(OH)3), which converts to CuO at 180 °C. Exploiting this reactivity, copper nitrate can be used to generate nitric acid by heating it until decomposition and passing the fumes directly into water. This method is similar to the last step in the Ostwald process. The equations are as follows:
2 Cu(NO3)2 → 2 CuO + 4 NO2 + O2
3NO2 + H2O → 2HNO3 + NO
Natural basic copper nitrates include the rare minerals gerhardtite and rouaite, both being polymorphs of Cu2(NO3)(OH)3 substance.
Structure
Anhydrous copper(II) nitrate
Anhydrous copper(II) nitrate has been crystallized in two solvate-free polymorphs. α- and β-Cu(NO3)2 are fully 3D coordination polymer networks. The alpha form has only one Cu environment, with [4+1] coordination, but the beta form has two different copper centers, one with [4+1] and one that is square planar. The nitromethane solvate also features "[4+ 1] coordination", with four short Cu-O bonds of approximately 200 pm and one longer bond at 240 pm. They are coordination polymers, with infinite chains of copper(II) centers and nitrate groups. In the gas phase, copper(II) nitrate features two bidentate nitrate ligands (see image at upper right). Thus, evaporation of the solid entails "cracking" to give the copper(II) nitrate molecule.
Hydrated copper(II) nitrate
Five hydrates have been reported: the monohydrate (Cu(NO3)2·H2O), the sesquihydrate (Cu(NO3)2·1.5H2O), the hemipentahydrate (Cu(NO3)2·2.5H2O), a trihydrate (Cu(NO3)2·3H2O), and a hexahydrate ([Cu(H2O)6](NO3)2). The hexahydrate is interesting because the Cu-O distances are all equal, not revealing the usual effect of Jahn-Teller distortion that is otherwise characteristic of octahedral Cu(II) complexes. This non-effect is attributed to the strong hydrogen bonding that limits the elasticity of the Cu-O bonds.